1. Field of the Art
The present invention relates to an apparatus for detecting a pulse wave produced from an arterial vessel of a subject.
2. Related Art Statement
There is known a pulse wave detecting apparatus including (1) a pulse wave sensor having a press surface on which one or more pressure sensing elements are provided, the pulse wave sensor being pressed against an arterial vessel of a subject via a body surface above the arterial vessel so that the one or more pressure sensing elements detect a pulse wave produced from the arterial vessel of the subject, (2) pressing means for pressing the pulse wave sensor against the arterial vessel via the body surface, while varying the pressing force over a predetermined force range, and (3) means for determining an optimum, pulse wave sensor pressing force based on the pulse wave (pulses of the pulse wave) which is detected by the one or more pressure sensing elements while the pressing force is varied, and (4) means for obtaining a pulse wave of the subject through the pulse wave sensor pressed with the thus determined optimum pressing force. The conventional apparatus determines as the optimum pulse wave sensor pressing force a pressing force at which the pulse wave sensor (one or more pressure sensing elements) detects a pulse of the pulse wave whose amplitude is maximum, namely, the greatest of the amplitudes of the pulses detected by the pulse wave sensor in the process of varying the pressing force.
However, generally the thus determined optimum pressing force does not fall to around the middle value of a pressing force range which covers pressing force values at which a pulse wave having a sufficiently great amplitude is detected. Accordingly, in the event that the pulse wave sensor pressing force is changed from the optimum pressing force to a greater or smaller value due to physical motion of the subject or other causes, the conventional apparatus may fail to detect a pulse wave having a sufficiently great amplitude.